Effect of Applied AC Voltage on the Performance of Non-Faradaic Impedimetric Biosensors

Electrochemical impedance spectroscopy based non-faradaic biosensors are promising low-cost and rapid detection tool for a variety of biomarkers. Unlike faradaic impedimetric biosensors, non-faradaic impedimetric biosensors are redox-free and do not require the use of three electrodes. Instead, two electrodes are enough to carry out biosensing using non-faradaic biosensors. Commonly used AC perturbation during non-faradaic impedimetric biosensors is 10 mV to maintain the linearity of the electrochemical biosensor. In this work, we investigated the effect of different AC voltages (10, 50, 100, 200, 400, 800 and 1600 mV) on bare gold interdigitated electrodes (Au-IDEs). As the AC voltage increased, the capacitance and phase of bare Au-IDEs increased whereas the impedance decreased. At 800 and 1600 mV, non-linear effects started to appear on the Lissajous plots. Then, the effect of all the AC voltages except 800 and 1600 mV on the performance of fully functionalized non-faradaic LDL-cholesterol sensors were investigated. Increasing the AC voltage resulted in better limit of detection and change in capacitance. However, it also resulted in larger change in capacitance due to testing against negative (control samples). The reported study can be useful for the future development of non-faradaic impedimetric biosensors for the detection of different biomarkers and to achieve different limits of detection as per the application requirements.